Help?

[VVVCCCEEE]

3a? Thank you

[Pathfinder]

There are a two important bits of information given to us in the background information which will help to get an answer:
1) The base of the box is square (the length of the sides are equal).
2) h cm is the height.
This means that our box has a square base with length x (length is the same on all sides of a square) and 4 rectangular sides with lengths x and height h (all sides must have height = h or else it wouldn't really be a proper box).

With questions like these, its best to draw a diagram, look to the one attached for an example.
Using the diagram, we can see that:
Area of Square Base = x²
Area of Side = l*w = x*h

We simply add all the areas to get the total outside surface area (TOSA) - remember there are four sides and they must be accounted for in our final equation - we just multiply x*h by 4.

Therefore, TOSA = x² + 4x*h.

Hope this helps!
Pathfinder.